This invention relates to release agents of the type which are of wax materials, and, more particularly, to a release agent as disclosed in U.S. Pat. No. 2,735,354. More particularly, the use of ethylene bis-stearamide, commonly called Acrawax, as supplied by Glyco Chemicals. While the prior art calls for application of the wax in combination with enamel or lacquer as a dispersion or suspension or by independent swabbing, dipping or fusion coating, those techniques are unsatisfactory and difficult. In particular, the prior art techniques have drawbacks which result in the application of too much Acrawax release agent in a uniform and poorly located coating some of which is inside of the container, on the packed material and on the container tooling.
The combination of the release agent and coating lacquer or enamel has proven to be energy intensive in that the heat required to dry the lacquers and enamels is added to the heat required to fuse the release agent carried in dispersion or suspension. Moreover, the technique of applying the release agent with the lacquer or enamel relies entirely upon the fact that the wax will bloom to the surface during curing. This result is uncertain and as such the coating properties that are particularly desirable for use as a can liner are incompatable in combination with such release agents. For instance, particular coatings that polmerize during curing can be adversely affected such that uniform cross-linking and/or curing does not take place. The result is an uncross-linked oligomer which is not FDA approved and as such is unusable for packing comestibles and the like.
The preparation of containers by coating at high-speed for purposes of providing a low cost package for comestibles and the like requires a uniform, reliable and repeatable processing. It is necessary to be able to apply and cure the coatings in a very brief time span. The addition of the release agent to the coating interfers with the high-speed application and curing of the coating by lengthening the curing times. Consequently, the requisite blooming of the release agent to the surface will not occur. A coating that has Acrawax in it can not be coil coated since such a process does not bring as much to the surface as, for example, sheet baking of coated sheets. Consequently, products that stick like chicken and turkey require additional Acrawax to achieve release.
Thus, it is desired to apply the combination of the coating and the release agent to the sheet stock before forming in order to insure uniform high-speed application, low cost and simplicity of machinery. However, it has been found that the combination once cured tends to interfere with forming tools which are necessary to draw the strip into a container. More particularly, the release agent which tends to be a hard wax material collects on the tooling and because of its consistency and tenacity interfers with the efficient operation of the tooling in that the tools have to be stopped and cleaned in order to maintain their smooth operation and to maintain the dimensional tolerances of the containers. Moreover, the wax buildup tends to attract dirt and particles in the environment which build up in the recesses and crevices of the tooling interferring with the proper forming of the containers and leaving undesirable deposits in the newly formed containers. Wax buildup prevents the tools from attaining their desired stroke resulting in deformed or misformed containers which do not have the designed shape or the desired strength. A package which will not meet its designed properties is unacceptable in connection with the packing of comestibles and the like because any visible exterior failure requires that the packed food be thrown away even though it may be good. The cost of checking outweighs the price of the product and the risk outweighs both.
The materials used for release agents are granular in form and are about the size of finely ground corn meal having the hardness of very hard wax material. As such, it is not easily handled for application of thin coatings as necessary for use as a release agent on the inside of a container. More particularly, it is now shown in the prior art, how a granular material of this type can be applied uniformly to the inside of a formed container at high speeds. For example, such wax has poor solubility in ordinary solvents and even if made soluble, the problem of solvent fumes remains. While the material is also supplied in a micronized powder having a 12 micron powder size, it is more costly to buy the material that way and such material is supplied for the purpose of dispersion or suspension in the enamel or lacquer. Equipment capable of applying such coatings at the speeds and the thicknesses necessary with effective release agent properties is not available for use in connection with either the micronized or the granularized particles.